Mamma Mia! The songbooks of everyone from Billy Joel to Queen are being turned into musicals

Poor Paul Simon. A few years ago he had the fool idea that a rock composer who wants to make it on Broadway has to go out and actually write new music. He spent years working on his musical The Capeman, only to see it bomb with the critics and at the box office.

Abba had it so much easier. The Swedish rock group (whose leaders, Benny Andersson and Bjorn Ulvaeus, had been burned on Broadway once before, with their 1988 musical Chess) simply sat back and let a bunch of other folks take Abba's hit songs, graft them onto a...